Hmm, 548 grams para sa 5 months and 5 days seems a bit light, mama, usually by that point babies should be closer to 700+ grams na depende sa genetics at nutrition mo. Best thing is to follow up with your OB agad para ma-check properly, kasi sometimes the ultrasound measurements can vary, and they'll want to make sure baby's growing well at walang concerns sa placenta or amniotic fluid. One of my mum friends had a similar situation and after follow-up ultrasound and proper monitoring, lahat naman naging okay, so don't panic muna pero huwag din i-delay ang check-up, okay?